The purpose of this Core is to provide a consistent preparation of animal models across the various projects. It will be the responsibility of this Core to prepare the chronic animal models for the individual investigators. This will reduce the variability of preparations and will release the individual project directors from the extremely labor intensive task of creating these preparations and care for their immediate post operative recovery. The various animal models will be prepared by or under the director of Dr. Cornish who has had many years of experience in the preparation of chronic animals and is experienced in these specific animal preparations. We will be assisted by two technicians in the preparation and care of the animals prior to their use by the various investigators. The models prepared by this core will be (1) the coronary ligation model of heart failure (HF) in the rat, () the pacing model of HF in the rabbit, and (3) the pacing model of HF in the dog.